The term “struggling” writer really applies to every single human being. We have all struggled with writing at some point and will continue to struggle moving forward. The difference between successful writers and unsuccessful writers (“success” being defined as students who turn in completed essays that convey meaning effectively versus those who do not) lies in being able to work through frustration.
Writing is a process. It is recursive. No piece of writing is ever "final." Something can always be better. I often feel this way whenever I read back over my own old essays and inevitably find a sentence that could be better, a paragraph that could be stronger, or a word that could be more precise.